Note: Descriptions are shown in the official language in which they were submitted.
~78~
SP~CIFICATION
Title of the Invention:
Flame retardant polyolefin composition
Field of the Invention:
This invention relates to polyole~in compositions
having high flame-retardancy. More particularly, it
relates to polyolefin composition having superior mechan-
ical properties,processability and flame retardancy which
is obtained as its characteristic feature of production
process, by blending polyolefin resin, a halogen-containing
flame retardant, antimony trioxide, a crosslinking agent
and a radical generating agent or by blending polyolefin
resin, a halogen~containing flame retardant, antimony
trioxide, a boron compound, a crosslinking agent and
a radical generating agent and subjecting the resultant
mixture to melting and kneading treatment, or by blending
a halogen-containing flame-retardant, antimony trioxide
or a halogen-containing flame-retardant, antimony trioxide
and a boron compound with a polyolefin resin having been
subjected to the melting and kneading pretreatment with
said crosslinking agent and a radical generating agent.
Description of the Prior Art:
On account of superiority of processability, chemicals-
resisting proper~y, weatherability, electrically charac-
teristic properties, etc., polyolefin resin is widely used
F ~
.
7~ 8
in various fields including electric household appliances.On the other hand it has drawback in that it is extremely
inflammable, liquefied once by pyrolysis at the -time of
combustion, dropping of liquid drops formed with flaming
or without flaming combustion, falling of burnt pieces
cut by fusion (hereinafter -these dropped or fallen mate-
rials will be referred to as drip and drip forming
property as dripping property). Whether drip is existing
or not is one of the important fac-tors for evaluating
flame~retardancy. Even when a resin is superior in self-
extinguishing property, its flame-retardancy is ranked in
a lower grade if it has drip. Thus an improvement of
dripping property is one of the important problem in
the point of flame-retarding technique of said resin.
Further, since polyolefin resin has relatively higher
crystallinity and non-polar property, it is inferior to
in compatibility with a flame-retardant and shows a great
reduction of physical properties by addition of a flame-
retardant. On this account, for flame retardancy or
retardance of polyolefin resin, there has been made
heretofore various kind of proposal.
As general methods for making flame retardan-t
polyolefin composition, a simultaneous use of an organic-
~logen-containing flame-retardant with a certain kind of
25 metal oxide (Japanese patent publication of 25061 of 1976)
~7~
-- 3
and addi-tion of a nitrogen containing compound, a boron-
containing compound or a water-containing inorganic
compound, as a flame-retardant have been prevailing.
However,an organic halogen-containing flame-retardant
S is superior in self-extinguishing property but has
drawback in that drip is formed at the time of burning.
On the other hand, an inorganic flame-retardant e.g.
magnesium hydroxide is superior in dripping property,
and has a certain extent of self-extinguishing property
but has drawback because for providing a high level of
flame-retardancy, a large amount of addition is necessary.
A polyolefin composition containing a large amount of
incorporated inorganic compound has drawback in the point
of deterioration of processing characteris-tics due to
the reduction of fluidity of molten material and reduction
of mechanical properties of formed articles when said
composition is used in forming. The range for addition
is limitative in practical use because of reduction of
mechanical strength of formed articles and attainment of
high level of flame-retardancy is difficult.
In order to overcome these drawbacks, i-t has been
proposed to use simultaneously a bromine-containing flame
retardant and borofluoride salt to polypropylene resin
(Japanese laid open application No. 163937 of 1979);
to mix ethylene-propylene rubber modified with silane
-- 4
compound and a flame-retardant with polyethylene resin,
followed by crosslinking with an organic peroxide (Japanese
laid open patent application No. 110139 of 1980); to use
simultaneously a silane coupling agent, ethylene-
propylene rubber, chlorinated polyethylene and a flame-
retardant in forming, followed by crosslinking with water
(Japanese laid open patent application No. 45716 of 1980).
However, according to the above-mentloned Japanese laid
open application No, 163937 of 1979, the improvement of
dripping property is still not in the state which can be
said to be sufficient, the processes of Japanese laid open
patent application No. 110139 of 1980 and No. 45716 of
1980 are those which have been applied to polyethylene,
which create crosslinking very easily in the presence of
an organic peroxide.
Summary of the Present Invention:
-
The inventors of the present invention concentratedtheir effort in solving the above-mentioned problem relat-
ing to flame-retardant polyolefin compositions. As the
result, they succeeded in obtaining flame~retardant
- polyolefin compositions which improve mechanical strength
of formed articles, greatly improve dripping property at
the time of burning, further improve drawdown of burnt
resin pieces by melting and falling in drops of burnt
r,esin pieces by incorporating a crosslinking agent and
- 5 - ~ ~ ~8~
a radical generating agent to a polyolefin re3in in the presence
of a halogen-containing flame-retardant and antimony trioxide
or in the presence of a halogen-containing flame-retardant,
antimony trioxide and a boron compound and ~ubjecting the
resulting mixture to melting and kneading treatment or mixing
a halogen-containing flame-retardant and antimony trioxide
or a halogen-containing flame-retardant, antimony trioxide
and a boron compound with a polyolefin resin having been, in
advance, tr0ated with a crosslinking agent and a radical
generating agent and subjecting the resulting mixture to
melting and kneading treatment and completed the present
invention.
As evident from the foregoing description, it i~
an object of the present invention to provide a flame-retardant
polyolefin composition which provides formed articles having
improved mechanical strength, and greatly improved dripping
property at the time of burning.
~ he above-mentioned object can be attained by a
flame-retardant polyprop~lene composition comprising following
components (A), (B~, (C), (D) and (E); (A) 0.1 - 1~5% by weight
of crosslinking agent relative to the total amount of the
components (A), (B), (C), (D) and (E) as 100% by weight, (B)
0~005 - 5% by weight of a radical generating agent relative
to the total amount of the all the components, (C) 5 - 60%
by weight of a halogen-containing flame-retardant selected
from the group compositing of decabromodiphenyl oxide and
ethylene-bis-tetrabromophthalimide, relative to the total
rm/
- 6 ~ 8~
amount of the all the components, (D) lO0 - 10% by weight of
antimony trioxide relative to the halogen-containing flame-
retardant, (E) balance of polypropylene re~in; the poly-
propylene resin being melted, and kneaded by the crosslinking
agent and the radical generating agent.
The above-mentioned object can alqo be attained by
a flame-retardant polypropylene composition comprising following
component~ (A), (B), (C~ / (D), (E) and (F); (A) 0.1 - 15% by
weight of crosslinking agent relative to the total amount of
the component~ (A), (B), (C), (D), (E) and (F) as 100~ by weight,
(B) 0.005 - 5% by weight of a radical generating agent relative
to the total amount of the all the component~, (C) 5 - 60%
by weight of a halogen-containing flame-retardant ~elected
from the group consisting of decabro~odiphenyl oxide and
ethylene-bis-tetrabromophthalimide, relative to the total ~mount
of the all the components, (D) 100 - 10% by weight, of antimony
trioxide relative to the halogen-containing flame-retardant,
(E) l - 10% by weight of a boron compound, (F) balance of
polypropylene resin, the polypropylene resin being melted and
kneaded by the crosslinking agent and the radical generating
agent.
Di~cussion of_the Detail~ and Preferred Embodiment of
the Invention
. . _
As polyolefin resina u~ed in the pre~ent invention,
a homopolymer of -olefin such as propylene, butylene or the
like, a random copolymer, a block copolymer consisting of
selected two or more members of ethylene, propylene and
1~
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- 7 - ~ ~ ~8~
butylene and ethylene vinylacetate copolymer, styrene-
butadiene copolymer,ethylene-propylene rubber and
a mixture of two or more of -these members can be mentione~.
Especially a polyolefin resin containing, as a main com-
ponent, polypropylene resin, is preferable.
As a halogen-containing flame-retardant, an aromatic
bromine compound having a melting point of 300CC or higher
e.g. decabromodiphenyl oxide, ethylene bis-tetrabromo-
ph-thalimide or the like is useful. Especially decabromo-
diphenyl oxide is preferably used.
The amount of addition of said halogen-containing
flame-retardant is in the range of 5 ~60~ by weight,
preferably 5 ~50% by weight, most preferably 7 -30~ by
weight.
The amount of addition of antimony trioxide is in
the range of 100 ~lO~ by weight based upon the above-
mentioned halogen-containing flame-retardant agent.
As crosslinking agent, polyfunctional monomers,
monofunctional monomers, oxim nitroso compound, maleimide
compound, silane coupling agent, etc. are used.
As concrete examples, there are, for example,
triallyl cyanurate, triallylisocyanurate, diethylene
glycol dimethacrylate, trimethylolpropane triacrylate,
trimethylolpropane trimethacrylate, pentaerythritol
triacrylate, pentaerythritol tetraacrylate, di~inylbenzene,
~ 8 - ~Z7~28
diallylphthalate, divinylpyridine, vinyltoluene, ethyl-
vinylbenzene, styrene monomer ~uinonedioxime, benzo-
quinonedioxime, p-nitrosophenol, etc~
The amount of addition of said crosslinking agent
is in the range of 0.1 ~15~ by weight, preferably 0.5 -10%
by ~Jeight,most preferably 1 ~6~ by weight.
As radical genera-ting agents, materials which generate
a radical by thermal decomposi-tion is useful. For example,
they are dicumyl peroxide; 2,5-dimethyl-2,5 di(t-bu-tyl
peroxy)hexane, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexyne
3; 1,3-bis(t-butylperoxyisopropyl)benzene; 1,1,4,4,7,7-
hexamethylcyclo 4,7-diperoxynonane; cumenehydroperoxide;
cumylperoxytrimethyl silane, etc.
The amount of addition of said radical generating
agent varies according to the kind of it, and it is in
the range of 0.005 -5~ by weight, particularly 0.01 ~1%
by weight.
As boron compounds, borax, borofluoride salt, for
example, sodium borofluoride, potassium borofluoride,
ammonium borofluorode are useful.
- The amoun-t of addition is in the range of 1 ~10% by
weight, preferably 1 ~8~ by weight, most preEerably 2 ~6
by weight.
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In the present invention, various kinds of addltives,
for example, antioxidant, lubricant, pigment, inorganic
filler (for example,calcium carbona-te, talc, clay, mica,
magnesium hydroxide, glass flbers, etc.) can be used
simultaneously.
In the production of the present composition, there
is no particular limitation in -the order of addition of
each component of the above~mentioned (A), (B), (C), (D)
and (E). Any of the following methods i.e. a method of
simultaneous mixing of (A), (B), (C), (D) and (E) followed
by melting and kneading; a method in which (A) and (B) are
added during the processing of melting and kneading of
(C), (D) and (E) and a method in which after melting and
kneading of (A), (B) and (E) in advance, (C) and (D~ are
mixed and melting and kneading are carried out subsequently.
Further, there is also no particular limitation in the
order of addition of each components of above-mentioned
(A), (s), (C), (D), (E) and (F). Any one of the following
methods i.e. a method in which (A), (s), (C), (D), (E) and
(F) are simultaneously mixed and subjected to melting and
kneading; a method in which after meltlng and kneading of
(A), (B) and (F) in advance, (C), (D) and (E) are mixed and
subjected to melting and kneading; or a method in which (A)
and (B) are added during the processing of mixing, melting
~nd kneading of (C), (D), (E) and (F) and further subjected
to melting and kneading, is applicable.
~ ~ .
~7~1Z8
- 10 -
As an apparatus for mixing the above-mentioned each
components, a common mixing apparatus such as a mixer
having an attached high speed stirrer e.g. Henschel mixer
(name of article of trade) ribbon blender, tumbler may be
useful. For melting and kneading, a common single or
-twin screw extruder can be used. Melting and kneading
temperature is in the range of 170C ~300C, preferably
200C ~260C. Retention time in the extruder of product
mixed by melting will be sufficient if a retention time
in a common extruder is used.
From the pellets of polyolefin composition, thus
obtained, test specimen of predetermined dimension were
molded and flame-retardancy and mechanical strength were
measured. With regard to flame retardancy, extremely better
flame-proofness and dripping property were indicated,
compared with comparative test specimens. Further, in
mechanical strength, flexural modulus, flexural strength,
tensile strength, Izod impact strength, the test specimen
show higher numerical values in all these tests compared
with comparative test specimen and it has been revealed
that increase of mechanical strength of formed articles
as well as improvement of a large extent of flame-
retardancy and dripping property can be attained.
The present invention will be more concretely
illustrated by referring to specific examples and
7~
Comparatlve exmaples. Burni~g tests in the specific
examples and Comparative examples were carried out
according to the following method. Further the measure-
ments of mechanical strength were carried out according
to the method of JISK 6758-1981.
Burning test
Test specimens having a length of 127 mm, a width of
12.7 mm and a thickness of 0.8 mm were vertically suspended
by fixing at the top end in a room in which there is no
movement of air. A flame of Bunsen burner having been
controlled to produce a 19 mm blue flame was applied to
a test specimen from its lower end fo-r 10 seconds. After
10 seconds, the burner was removed and a time at which
the test specimen continues to burn with flaming after
removal of the burner, was measured and this is recorded
as the first flaming combustion time. Immediately after
extinguishment of test specimen, a blue flame of burner
was applied again to the test specimen at its lower end
according to the same method for 10 seconds and a time
elapsed until extinguishment was attained agaln was
measured and this is recorded as the second flaming
combustion time. Subsequently a time during which the
- test specimen is burning with glowing combustion is also
measured. This time are summed up with the above-mentioned
- 25 second ~laming combustion time and recorded as a gLow time.
- 12 ~
Further, cotton is placed at the position 305 mm below
the test specimens and observed whether it catches fire
by flaming drip during the testing time and the result
is recorded. Foregoing tests were carried out by using
5 test specimens and fire-retardancy was evaluated.
Specific examples 1 ~2 and Comparative examples 1 -3
After definite amounts of a halogen-containing
flame-retardant, an-timony trioxide, a crosslinking agent,
and a radical generating agent having the details described
in Table 1 were mixed with, as polyolefin resin, ethylene-
propylene block copolvmer having a melt flow rate (M.F.R.)
of 2.5 g/10 min. (the extruded amount of melted resin
for 10 minutes at the time when 2.16 Kg of load is applied
at 230C) and ethylene content of 12% by weight or a pro-
pylene homopolymer having a M.F.R. of 2.0 g/10 min. themixture was melted and kneaded (mean retention time of
25 sec.) at 230C by using a twin screw extruder having
a diameter of 45 mm (Brand PCM-45 of Ikegai Tekkosho K.K.)
to do pelletizing. As Comparative examples 1 ~3~ each of
the components described in Table 1 was mixed, melted, and
kneaded according to the method the same as that of E~amples
1 -2 to do pelletizing. Resulting pellets were charged to
an injectlon molding machine to mold -test specimen of
definite dimension, which were subjected to the measurement
o~ flammability and mechanical strength. The result are
shown in Table 1.
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As evident from Example l, Comparative examples 1 ~2
those which did not use a crosslinking agent and a radical
generating agent were not extinguished as in Comparative
example and fall of drip with flaming combustion was
observed. Further, those in which the amount of a flame-
retardan-t and antimony trioxide were increased, were
satisfactory in combustion time but melting and falling
of test specimens were observed by the second combustion.
In contrast, Example 1 showed excellent extinguishment and
dripping property in spite of i-ts same amounts of addition
of the flame-retardant and antimony trioxide as in Compara-
tive example l. Particularly, at the second combustion
time, notable difference in dripping property was observed.
Further, as for mechanical strengths, higher numerical
values were indicated in flexural modulus, flexural
strength, tensile strength, Izod impact strength, etc.
compared with those of Comparative example 1.
In specific example 2, a propylene homopolymer having
a melt-flow rate 2.0 g/10 min. was used as a polyolefin
resin and subjected to similar tests but it was revealed
that a great extent of flammability and dripping property
were improved at the time of the second combustion as
compared with those of Comparative example 3.
Examples 3 ~4 and Comparative examples 4 ~ 7
- To polypropylene homopolymer having a M.F.R. of 2.0 g/
lO min., as a polyolefin resin, a halogen-containing
16 ~ 28
flame-retardant, antimony trioxide, a crosslinking agent
a radical generating agent, and a boron compound, the
details of whi.ch are described in Table 2, each in
deEinite amounts were admixed in a Henschel mixer (FM-75C
manufactured by Mitsui Miike Seisakusho), and thereafter
by using a twin screw extruder having a diameter of 45 mm
(PCM-45, of Ikegai Tekko K.K.), melting and kneading were
carried out at 230C (mean retention time in the extruder
25 sec.) to effect pelletizing. As Comparative examples
4 -7, each of the components described in Table 2 were
mixed, melted and kneaded according to the method the same
with those of Examples 3 ~4, to effect pelletizing.
~esulting pellets were charged to an injection molding
machine to mold into test specimen of definite dimension
at a temperature of 250C, and the molded test specimens
were subjected to the measurement of flammability and
mechanical strength. The results of these tests are shown
in Table 2.
Examples 5 _ 9 and Comparative examples 8 ~9
By using, as polyolefin resin, an ethylene-propylene
block copolymer having a M.F.R. of 2.5 g/lO min. and
further using, in Examples 6 ~7, as inorganic filler, talc
and wollastonite, definite amounts of each of the components
the detail of which are described in Table 3, were mixed,
melted and kneaded according to a method similar to -that
of specific examples 3 ~4 to effect pelletizing.
- 17 - ~7~
By using the resulting pellets, test specimen of
definite dimension were molded according to a method
described in specific examples 3 ~4 and measurements of
flammability and mechanical strength were conducted.
The results of these tests are indicated in Table 3.
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~7~
As understandable from -the description of Table 2,
it can be seen that extinguishing property, glow time and
dripping property are all greatly improved. Namely, as
indicated in Comparative example 6, simple increase of
the amount of a halogen-containing flame-retardant and
antimony trioxide provides good extinguishing property
but melt-falling of test specimen were observed and
dripping property was not improved at all. It can be
seen that those in which combination same wi-th that of
specific example 3 was made except that a crosslinking
agent and a radical generating agent as in Comparative
example 4 were not added, did not show extinguishment and
melt fallen materials were observed, and it is observed
that neither extinguishing property nor dripping property
was improved. Those in which addition of a halogen-
containing flame retardant and antimony trioxide was
merely increased, relative to Comparative example 4 as
in Comparative example 7 improves extinguishing property
but melt falling of test specimen was observed and dripping
property was not improved. Further, in a system in which
a boron compound was removed from specific example 3, as
in Comparative example 5, extinguishment property and
dripping property showed satisfactory result but a glow
time was considerably longer. The first goal of this glow
time is 30 seconds or less and the second goal is 60 seconds
7~
- 23 -
or less but considering from these results, it cannot be
said that this system is satisfactory. Whereas it has
been revealed that extinguishment property, glow time
and dripping property were all improved. Further,
specific example 4 is directed to a case where ethylene
bis~tetra~bromophthalimide)was used as a halogen
containing flame-retardant but extinguishment property
and dripping property are improved.
Referring now Table 3, specific example 5 is directed
to a case where an ethylene propylene block copolymer
having an ethylene content of 12~ by weight (M.E'.R. 2.5 g/
10 min.) was used as a polyolefin resin and showed good
extinguishment, glow time and dripping property, similarily
as in specific example 3. Comparative example 8 is
lS directed to a case where only a radical generating agent
is removed from specific example 5 but it is seen that
both extinguishment and dripping property were worse and
the effectiveness of a crosslinking agent is not exhibited
due to the non-existence of a radical generating agent.
It is observed that simple increase of the amounts of
a halogen-containing flame-retardant, and antimony trioxide,
makes extinguishment better similarily as in Comparative
example 7, melt-falling of test specimens were observed.
Further, specific examples 6 _7 correspond to the cases
where an inorganic filler are added to specific example 5.
- 24 -
Self-extinguishment and dripping property were good but
a glow time is inferior to specific example 5 to some
extent. Specific example 8 is directed to a case where
pentaerythrltol triacrylate is used as a crosslinking
agen-t and example 9 is directed to a case where borax is
used as a boron compound and it has been revealed that
superior extinguishment, dripping property and glow time
were exhibited as in specific example 5.
